UC3842B, 43B UC2842B, 43B

9

MOTOROLA ANALOG IC DEVICE DATA

+

–

Reference

Regulator

VCC

UVLO

+

–

Vref

UVLO

3.6V

36V

S

R

Q

Internal

Bias

+ 1.0mA

Oscillator

2.5V

R

R

R

2R

Error

Amplifier

Voltage

Feedback

Input

Output/

Compensation

Current Sense

Comparator

1.0V

VCC

7(12)

Gnd

5(9)

VC

7(11)

Output

6(10)

Power Ground

5(8)

Current Sense Input

3(5)

RS

Q1

VCC

Vin

1(1)

2(3)

4(7)

8(14)

RT

CT

Vref

= Sink Only Positive True Logic

Pin numbers adjacent to terminals are for the 8–pin dual–in–line package.

Pin numbers in parenthesis are for the D suffix SO–14 package.

Figure 17. Representative Block Diagram

Figure 18. Timing Diagram

Large RT/Small CT

Small RT/Large CT

PWM

Latch

(See

Text)

Capacitor CT

Latch

“Set” Input

Output/

Compensation

Current Sense

Input

Latch

“Reset” Input

Output